A spring-force drive for a vacuum power switch for medium-high voltage is described in the Calor-Emag reports I/II/1986 on pages 9 to 12. This known spring-force drive has a drive shaft which is driven by a spiral spring for switching the power switch on and off in the same direction of rotation. On the drive shaft there is mounted, fixed in terms of rotation, a support disk with two support surfaces which cooperate in the switch-on or switch-off position of the drive shaft with a stationary, swivel-mounted support member. On the drive shaft there is also mounted, fixed in terms of rotation, one cam disk each per pole, the circumferential surface of which cam disk forms a control cam for a follower roller arranged at one end of a swivel lever. The other end of the swivel lever is connected via a contact compression spring arrangement to the movable switch contact of a vacuum switch tube. A switch-off spring also acts on the swivel lever, which switch-off spring also presses the follower roller against the circumferential surface of the cam disk. To switch on the power switch the support member releases the support plate and thus the drive shaft for a rotation through 270.degree., whereby the movable switch contact is brought, via the cam disk acting the terms of pressure on the follower roller and via the swivel lever, into the switch-on position. In this respect, both the contact compression spring arrangement and the switch-off spring are tensioned. In order to switch off the power switch the support member releases the support disk for a rotation of 90.degree.. In this respect, the swivel lever and the movable switch contact are brought back into the switch-off position by the switch-off spring in accordance with the shape of the circumferential surface, the movement of the swivel lever being determined by the cam disk, against the circumferential surface of which the follower roller is pressed by the switch-off spring. In order to ensure reliable switching-off, in each case, even with soldered switch contacts, the switch-off springs are dimensioned to be considerably stronger than would be necessary to achieve the required speed of the movable switch contact. This requires that large amounts of energy have to be made available for the switching, which brings about large forces in the drive and a corresponding dimensioning.